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Creating Avian Forebrain Chimeras to Assess Facial Development

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Published on: February 18, 2021

Flightlessness affects cranial morphology in birds.

Sander W S Gussekloo¹, Jorge Cubo

¹Experimental Zoology Group, Wageningen University, de Elst 1, NL-6708 WD Wageningen, The Netherlands. Sander.Gussekloo@wur.nl

Zoology (Jena, Germany)

|January 23, 2013

Summary

Flightlessness in birds influences skull shape, with heavier skulls potentially evolving due to relaxed selection for lightness. This study reveals distinct cranial morphology in flightless birds compared to their flying relatives.

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Area of Science:

Evolutionary Biology
Comparative Anatomy
Paleontology

Background:

Flightless birds across different evolutionary lineages exhibit shared traits in their pectoral and pelvic structures.
Existing research suggests that the absence of flight may also impact the morphology of avian skulls.

Purpose of the Study:

To investigate the correlation between flightlessness and cranial morphology in modern bird species.
To explore the developmental basis of skull differences in flightless birds.

Main Methods:

Utilized discriminant analyses and variation partitioning on a large sample of flightless bird species.
Compared the ontogenetic development of the chicken skull (Gallus) with the adult morphology of various flightless birds.

Main Results:

Statistical analyses confirmed a significant relationship between skull morphology and the flightless condition in birds.
Palaeognathous flightless birds (ratites) displayed skull morphologies dissimilar to juvenile chickens, suggesting peramorphosis.
Neognathous flightless birds' skull morphologies fell within the range of chicken development, yielding no definitive conclusions on their ontogeny.

Conclusions:

Flightlessness in birds is associated with altered cranial morphology, possibly due to reduced selective pressure for lightweight skulls, allowing for increased muscle mass.
The developmental pathways for skull morphology in flightless birds may differ, with some exhibiting overdevelopment (peramorphosis) compared to flying ancestors.